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.TH T_RCVVUDATA 3NSL "May 7, 1998"
.SH NAME
t_rcvvudata \- receive a data unit into one or more noncontiguous buffers
.SH SYNOPSIS
.LP
.nf
#include <xti.h>



\fBint\fR \fBt_rcvvudata\fR(\fBint\fR \fIfd\fR, \fBstruct t_unitdata *\fR\fIunitdata\fR, \fBstruct t_iovec *\fR\fIiov\fR,
     \fBunsigned int\fR \fIiovcount\fR, \fBint *\fR\fIflags\fR);
.fi

.SH DESCRIPTION
.sp
.LP
This function is used in connectionless mode to receive a data unit from
another transport user.  The argument  \fIfd\fR identifies the local transport
endpoint through which data will be received,  \fIunitdata\fR holds information
associated with the received data unit,  \fIiovcount\fR contains the number of
non-contiguous udata buffers which is limited to  \fBT_IOV_MAX,\fR which is an
implementation-defined value of at least 16, and  \fIflags\fR is set on return
to indicate that the complete data unit was not received.  If the limit on
\fIiovcount\fR is exceeded, the function fails with \fBTBADDATA\fR.  The
argument  \fIunitdata\fR points to a  \fBt_unitdata\fR structure containing the
following members:
.sp
.in +2
.nf
struct netbuf addr;
struct netbuf opt;
struct netbuf udata;
.fi
.in -2

.sp
.LP
The  \fImaxlen\fR field of  \fIaddr\fR and  \fIopt\fR must be set before
calling this function to indicate the maximum size of the buffer for each. The
\fIudata\fR field of  \fBt_unitdata\fR is not used. The  \fIiov_len\fR and
\fIiov_base\fR fields of "\fIiov\fR\fB0\fR" through  \fIiov [iovcount-1]\fR
must be set before calling  \fBt_rcvvudata()\fR to define the buffer where the
userdata will be placed.  If the maxlen field of  \fIaddr\fR or  \fIopt\fR is
set to zero then no information is returned in the  \fIbuf\fR field for this
parameter.
.sp
.LP
On return from this call,  \fIaddr\fR specifies the protocol address of the
sending user,  \fIopt\fR identifies options that were associated with this data
unit, and  \fIiov\fR\fB[0]\fR\fI\&.iov_base\fR through \fIiov
[iovcount-1].iov_base\fR contains the user data that was received. The return
value of  \fBt_rcvvudata()\fR is the number of bytes of user data given to the
user.
.sp
.LP
Note that the limit on the total number of bytes available in all buffers
passed:
.sp
.in +2
.nf
\fIiov(0).iov_len + . . + iov(iovcount-1).iov_len\fR)
.fi
.in -2

.sp
.LP
may be constrained by implementation limits. If no other constraint applies, it
will be limited by \fBINT_MAX\fR. In practice, the availability of memory to an
application is likely to impose a lower limit on the amount of data that can be
sent or received using scatter/gather functions.
.sp
.LP
By default,  \fBt_rcvvudata()\fR operates in synchronous mode and waits for a
data unit to arrive if none is currently available.  However, if
\fBO_NONBLOCK\fR is set by means of \fBt_open\fR(3NSL) or \fBfcntl\fR(2),
\fBt_rcvvudata()\fR executes in asynchronous mode and fails if no data units
are available.
.sp
.LP
If the buffers defined in the  \fIiov[]\fR array are not large enough to hold
the current data unit, the buffers will be filled and  \fBT_MORE\fR will be set
in flags on return to indicate that another  \fBt_rcvvudata()\fR should be
called to retrieve the rest of the data unit.  Subsequent calls to
\fBt_rcvvudata()\fR will return zero for the length of the address and options,
until the full data unit has been received.
.SH RETURN VALUES
.sp
.LP
On successful completion,  \fBt_rcvvudata()\fR returns the number of bytes
received. Otherwise, it returns  -1 on failure and \fBt_errno\fR is set to
indicate the error.
.SH VALID STATES
.sp
.LP
\fBT_IDLE\fR.
.SH ERRORS
.sp
.LP
On failure, \fBt_errno\fR is set to one of the following:
.sp
.ne 2
.na
\fB\fBTBADDATA\fR\fR
.ad
.RS 15n
\fIiovcount\fR is greater than  \fBT_IOV_MAX.\fR
.RE

.sp
.ne 2
.na
\fB\fBTBADF\fR\fR
.ad
.RS 15n
The specified file descriptor does not refer to a transport endpoint.
.RE

.sp
.ne 2
.na
\fB\fBTBUFOVFLW\fR\fR
.ad
.RS 15n
The number of bytes allocated for the incoming protocol address or options
(\fImaxlen\fR) is greater than  \fB0\fR but not sufficient to store the
information.  The unit data information to be returned in \fIunitdata\fR will
be discarded.
.RE

.sp
.ne 2
.na
\fB\fBTLOOK\fR\fR
.ad
.RS 15n
An asynchronous event has occurred on this transport endpoint and requires
immediate attention.
.RE

.sp
.ne 2
.na
\fB\fBTNODATA\fR\fR
.ad
.RS 15n
\fBO_NONBLOCK\fR was set, but no data units are currently available from the
transport provider.
.RE

.sp
.ne 2
.na
\fB\fBTNOTSUPPORT\fR\fR
.ad
.RS 15n
This function is not supported by the underlying transport provider.
.RE

.sp
.ne 2
.na
\fB\fBTOUTSTATE\fR\fR
.ad
.RS 15n
The communications endpoint referenced by \fIfd\fR is not in one of the states
in which a call to this function is valid.
.RE

.sp
.ne 2
.na
\fB\fBTPROTO\fR\fR
.ad
.RS 15n
This error indicates that a communication problem has been detected between XTI
and the transport provider for which there is no other suitable XTI error
\fB(t_errno)\fR.
.RE

.sp
.ne 2
.na
\fB\fBTSYSERR\fR\fR
.ad
.RS 15n
A system error has occurred during execution of this function.
.RE

.SH TLI COMPATIBILITY
.sp
.LP
In the \fBTLI\fR interface definition, no counterpart of this routine was
defined.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7)  for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
MT Level	Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR fcntl (2),
.BR t_alloc (3NSL),
.BR t_open (3NSL),
.BR t_rcvudata (3NSL),
.BR t_rcvuderr (3NSL),
.BR t_sndudata (3NSL),
.BR t_sndvudata (3NSL),
.BR attributes (7)
